Natural products provide a wide range of biologically active agents, many of which have unique profiles of pharmacological activity and therapeutic potential. Over three hundred alkaloids have been identified in extracts from amphibian skins. These included batrachotoxins, which are potent activators of sodium channels, histrionicotoxins, which are noncompetitive blockers of nicotinic receptor channel complexes and of potassium channels, and pumiliotoxins, which have myotonic and cardiotonic activity due to inhibitory effects on closing of sodium channels. Further alkaloids included 2,5- disubstituted decahydroquinolines, 3,5-disubstituted indolizidines, 5,8- disubstituted indolizidines, 1,4-disubstituted quinolizidines, 3,5- disubstituted pyrrolizidines, pumiliotoxins, homopumiliotoxins and allopumiliotoxins, and tricyclic alkaloids, including pyrrolizidine oximes, pseudophrynamines, cyclopenta[b]quinolizidines, coccinellines, and the potent analgetic epibatidine. Most of these alkaloids have been detected and characterized from neotropical dendrobatid frogs. Pumiliotoxins, quinolizidines, indolizidines, pyrrolizidines and decahydroquinolines have now been characterized from bufonid toads of the genus Melanophryniscus and in mantellid frogs of the genus Mantella endemic to Madagascar. The latter contain a new class of alkaloids whose proposed dehydropumiliotoxin structure is being probed by synthesis. Pyrrolizidine oximes and coccinellines are derived in dendrobatid frogs from dietary insects by an extremely efficient alkaloid uptake process. Pyrrolizidine oximes and the potent analgetic epibatidine have been synthesized and are undergoing pharmacological study. Alkaloids, detected for the first time from birds, now include homobatrachotoxin, an anesthetic-like alkaloid, and an alkaloid with behavioral stimulant properties.